How surgical instruments are sterilized

STERILIZATION

Prior to operating surgical instruments are sent for sterilization which is a process / combination of processes in which the instruments are cleaned from all microorganisms like bacteria, viruses, fungi, etc.

Sterilization must not be confused with disinfection and sanitization because sterilization destroys all life where as the last two processes only selectively terminates the microorganisms.

Surgical instruments can be sterilized in several different ways. The three main methods used are:

    

• ETHYLENE OXIDE GAS STERILIZATION

• STEAM STERILIZATION

• RADIATION STERILIZATION

ETO gas sterilization:

In this process instruments are packed and placed in a vacuum chamber and Ethylene gas is then passed which destroys all the living organisms on the instrument. Ethylene oxide penetrates well, moving through paper, cloth, and some plastic films and is highly effective.

 Ethylene oxide sterilizers are used to process sensitive instruments which cannot be adequately sterilized by other methods. ETO can kill all known viruses, bacteria and fungi, including bacterial spores and is satisfactory for most medical materials, even with repeated use. However it is highly flammable, and requires a longer time to sterilize than any heat sterilizing treatment.

Steam sterilization:

Steam sterilization is also known as autoclaving. The instruments are placed (packed in layers of cloth) in pressure vessel and are exposed to saturated steam at 121°C for a minimum of 20 minutes. The elevated temperature and pressure destroys the cells of any living organism within the vessel.

Proper autoclave treatment will inactivate all fungi , bacteria, viruses and also bacterial spores , which can be quite resistant. It will not necessarily eliminate all prions .

Radiation sterilization:

Different radiations such as electron beam , X rays , gamma rays , or subatomic particles are used for the purpose. Radiation sterilization uses ionizing radiation to sterilize medical instruments. The radiation oxidizes any biological matter it comes into contact with, destroying its DNA, thereby sterilizing the instruments. This process is considered to be highly effective.

Other methods

Other heat methods include flaming, incineration , boiling, tyndalization, and  dry heat.

Flaming is usually used for the laboratory equipment not much for the surgical instruments.

Incineration   is done to burn the bio bastes from the Hospitals before mixing this to the nonhazardous wastes.

Boiling in water for fifteen minutes will kill most vegetative bacteria and inactivate viruses, but boiling is ineffective against prions and many bacterial and fungal spores; therefore boiling is unsuitable for sterilization. Boiling is a simple process, and is an option available to most people, requiring only water, enough heat, and a container that can withstand the heat; however, boiling can be hazardous and cumbersome.

Tyndalization  This is an up gradation of boiling process and involves boiling for a period (typically 20 minutes) at atmospheric pressure, cooling, incubating for a day,

•  again boiling, cooling, incubating for a day,
•  again boiling, cooling, incubating for a day,
•  and finally boiling again.

This is effective because many spores are stimulated to grow by the heat shock.  Tyndalization is ineffective against prions.

Dry heat is done in ovens up to a temp of 170 c for a period of 2 hrs. This process is mainly used for glass and metal objects i.e. cannot be used for plastic and rubber items.

• After sterilization all the instruments must be placed in an area free of dust, dirt, moisture etc.  as all these factors can affect the sterility.

• The shelf life of a sterilized item is also a very important factor to be considered. Any things such as  a tear in the wrapping , time elapsing, wetting  could allow the microorganisms to effect the sterilization.